On a weak Gauss law in general relativity and torsion

We present an explicit example showing that the weak Gauss law of general relativity (with cosmological constant) fails in Einstein-Cartan's theory. We take this as an indication that torsion might replace dark matter.Comment: 10 pages. Version 2 corrects a factor 3 in Cartan's equations to become

Determination of the zinc and cadmium contents in low-alloyed tin

The method of anodic linear sweep voltammetry (ALSV) has been used to determine the content of Zn and Cd (up to 4% w/w) in eutectic type binary alloys with Sn. The alloy samples were prepared by casting. The effect of the type and the pH of the electrolyte, as well as of the sweep-rate on the dissolution of Zn and Cd from the alloy during an anodic potentinal-sweep was investigated. It was shown that ALSV is sensitive to low concentrations of both Zn and Cd in the investigated alloys, as well-defined peaks of the dissolution of the two metals were recorded before the massive dissolution of Sn commenced. Well-defined linear dependencies between the quantities of electricity under the dissolution peaks of Zn (Qzn) or Cd (Qcd) and the respective contents of the metals in the alloys were found. Intercepts at the abscissa were found in both investigated systems indicating the formation of solid solutions from which neither Zn nor Cd could be eluted. In both alloys, the smallest amount of the alloying component which could be detected was 0.25% (w/w). The application of the ALSV method has several advantages over other analytical methods: it is non-destructive as the dissolution involves only a very thin layer of the alloy; it requires simple and cheap instrumentation; it is fast and relatively sensitive. These make it suitable for routine analysis

Miokardno premošćavanje prednje međukomorne arterije (r. interventricularis anterior) i njenih grana u malog zelenog majmuna (Cercopithecus aethiops sabeus)

Myocardial bridges (MBs) are structures consisting of heart muscle fibers running above the subepicardially positioned coronary arteries. In the light of previous studies, MBs are most often associated with the ramus interventricularis anterior (RIA) which put this vessel into the focus of our research. The purpose of the present study was to determine the frequency of occurrence and quantitative analysis of myocardial bridges over the RIA and its lateral branches. The studied material consisted of 55 Cercopithecus aethiops hearts, of both sexes, preserved in formaldehyde solution. Standard anatomical methods were used in the analysis, with the help of a stereomicroscope. The presence of MBs over the RIA was confirmed in a total of 70.9% samples, with no statistically significant differences related to the gender. In 2 hearts (3.6%) multiple bridges were revealed. The length of the bridges varies in the range of 0.5 mm - 31.6 mm, the distance from the origin of RIA varies between 0.5 mm - 25 mm which makes the proximal third of the anterior (paraconal) interventricular groove most frequently tunneled. The lateral branches of RIA were overbridged in 5.4%, with a single muscular band. The lenght of MBs varied from 6.2 mm - 12.5 mm, and they were localized over the first lateral branch in all cases.Fenomen miokardnog premošćavanja subepikardnih koronarnih krvnih sudova je proučavan na 55 srca malog zelenog majmuna (Cercopithecus aethiops sabeus). Koristeći standardne metode disekcije, identifikovali smo prisustvo miokardnih mostova (MM) na prednjoj međukomornoj arteriji (RIA) na 39 od 55 srca (70.9%), od kojih su 25 (71.4%) bila srca ženki, a 14 (70%) srca mužjaka, što nije pretstavljalo statistički značajnu razliku vezanu za pol (p>0.05). U najvećem broju slučajeva, 96.4% zabeležili smo jedan MM nad RIA, a samo na 2 srca (3.6%) RIA je bila premošćena sa dva MM. Ukupan broj MM u našoj seriji je 41, a njihova najčešća lokalizacija je proksimalna trećina krvnog suda. Dužina MM je varirala između 0.5 mm i 31.6 mm, a češće smo nalazili kraće strukture (do 15 mm). Udaljenost MM od mesta nastanka RIA je varirala od 0.6 mm do 25 mm. MM nad (levim) bočnim granama RIA (r. laterales) smo uočili na 3 od 55 srca (5.4%), i to na 2 srca ženki (5.7%) i na 1 srcu mužjaka (5%), što nije predstavljalo statistički značajnu razliku u odnosu na pol (p>0.05). Dužina MM je varirala od 6.2 mm do 12.5 mm. U svim slučajevim smo našli po jedan MM nad prvom bočnom granom RIA

Influence of Carbon Nanotubes on Polyamide Properties

In this study, the addition of carbon nanotubes (MWCNT) and modified carbon nanotubes (MWCNT-COOH) in the range of 0.5 wt. % to 5 wt. % in polyamide (PA) obtained as a residue upon 3D printing, was investigated. PA and nanocomposite samples were prepared by melt mixing. PA/MWCNT and PA/MWCNT-COOH nanocomposites were characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), THB thermal conductivity determination method, electrochemical impedance spectroscopy (EIS), and tensile test. Results of DSC analysis showed that both types of carbon nanotubes (MWCNTs) acted as nucleation centres of PA matrix, but had no effect on the order of the crystalline structure. Due to the polar nature of the surface and better dispersion, MWCNT-COOH filler accelerated PA crystallization more significantly compared to MWCNT. Due to the presence of nanofiller, the PA chains had limited motion space, which interfered with the crystallization process of the matrix. The thermal stability of the PA matrix increased with the addition of both MWCNT and MWCNT-COOH fillers. Higher thermal conductivity was achieved with the addition of MWCNT-COOH filler compared to the addition of MWCNT. The results of the tensile test showed that with the addition of both types of MWCNT fillers in the PA matrix, the modulus of elasticity and yield stress had reduced, but the yield strain increased. Results of the EIS showed that MWCNT nanofiller had not changed the electrical conductivity regardless of modification

Hamiltonian analysis of Poincar\'e gauge theory scalar modes

The Hamiltonian constraint formalism is used to obtain the first explicit complete analysis of non-trivial viable dynamic modes for the Poincar\'e gauge theory of gravity. Two modes with propagating spin-zero torsion are analyzed. The explicit form of the Hamiltonian is presented. All constraints are obtained and classified. The Lagrange multipliers are derived. It is shown that a massive spin-$0^-$ mode has normal dynamical propagation but the associated massless $0^-$ is pure gauge. The spin-$0^+$ mode investigated here is also viable in general. Both modes exhibit a simple type of ``constraint bifurcation'' for certain special field/parameter values.Comment: 28 pages, LaTex, submitted to International Journal of Modern Physics

Cfd simulations of thermal comfort in naturally ventilated primary school classrooms

The purpose of thermal comfort is to speck the combinations of indoor space environment and personal factors that will produce thermal environment conditions acceptable to 80% or more of the occupants within a space. Naturally ventilated indoors has a very complex air movement, which depends on numerous variables such as: outdoor interaction, intensity of infiltration, the number of openings, the thermal inertia of walls, occupant behaviors, etc. The most important mechanism for naturally ventilated indoors is the intensity of infiltration and thermal buoyancy mechanism. In this study the objective was to determine indicators of thermal comfort for children, by the CFD model based on experimental measurements with modification on turbulent and radiant heat transfer mathematical model. The case study was selected on school children of 8 and 9 years in "France Presern" primary school in Belgrade. The purpose was to evaluate the relationships between the indoor environment and the subjective responses. Also there was analysis of infiltration and stack effect based on meteorological data on site. The main parameters that were investigated are: operative temperature, radiant temperature, concentration of CO2, and air velocity. The new correction of turbulence and radiative heat transfer models has been validated by comparison with experimental data using additional statistical indicators. It was found that both turbulence model correct and the new radiative model of nontransparent media have a significant influence on CFD data set accuracy

Cfd simulations of thermal comfort in naturally ventilated primary school classrooms

The purpose of thermal comfort is to speck the combinations of indoor space environment and personal factors that will produce thermal environment conditions acceptable to 80% or more of the occupants within a space. Naturally ventilated indoors has a very complex air movement, which depends on numerous variables such as: outdoor interaction, intensity of infiltration, the number of openings, the thermal inertia of walls, occupant behaviors, etc. The most important mechanism for naturally ventilated indoors is the intensity of infiltration and thermal buoyancy mechanism. In this study the objective was to determine indicators of thermal comfort for children, by the CFD model based on experimental measurements with modification on turbulent and radiant heat transfer mathematical model. The case study was selected on school children of 8 and 9 years in "France Presern" primary school in Belgrade. The purpose was to evaluate the relationships between the indoor environment and the subjective responses. Also there was analysis of infiltration and stack effect based on meteorological data on site. The main parameters that were investigated are: operative temperature, radiant temperature, concentration of CO2, and air velocity. The new correction of turbulence and radiative heat transfer models has been validated by comparison with experimental data using additional statistical indicators. It was found that both turbulence model correct and the new radiative model of nontransparent media have a significant influence on CFD data set accuracy

Comparative analysis of objective techniques for criteria weighing in two MCDM methods on example of an air conditioner selection

This paper deals with comparative analysis of two different types of objective techniques for criteria weighing: Entropy and CRITIC and two MCDM methods: MOORA and SAW on example of an air conditioner selection. We used six variants for calculation of normalized performance ratings. Results showed that the decision of the best air conditioner was basically independent of the MCDM method used, despite the applied technique for determination of criteria weights. Complete ranking within all of the combinations of methods and techniques with diverse ratio calculation variants showed that the best ranked air conditioner was A7, while the worst ones were A5 and A9. Significant positive correlation was obtained for almost all the pairs of variants in all the combinations except for the MOORA - CRITIC combination with SAW - Entropy combination to have the highest correlations between variants (p < 0.01)

Activity of antioxidative defense enzymes in the blood of patients with liver echinococcosis

Background/Aim. Chronic echinococcocal disease is the parasite human disease caused by the penetration of larval (asexual) stages of the canine tapeworm (Echinococcus granulosus) in the liver of humans. After the penetration of the parasite, the host organism react by activating complement- depending immune response. The aim of this study was to elucidate the influence of larval form of Echinococcus granulosus in the liver on the activity of antioxidative defense enzymes in the blood of patients before and after the surgical intervention. Methods. We investigated the activity of antioxidative defense enzymes: copper/zinc containing superoxide dismutase (CuZn SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GR) and glutathione-S-transferase (GST) in the blood of patients before and after the surgical intervention in respect to the controls, clinically healthy persons. Results. Our results showed that the activity of the GSH-Px was significantly decreased in the plasma of the patients with echinocococal disease before the surgery in respect to the controls. The activity of GST was significantly higher in the blood of the patients after the surgery in comparison to the controls. Conclusion. Chronic liver echinoccocal disease caused significant changes of some antioxidative defense enzymes, first of all Se-dependent enzyme GSH-Px, which could be a suitabile biomarker in the biochemical evaluation of the disease. This work represents a first comprehensive study of the activity of antioxidative defense enzymes in cronic liver echinococcocosis in the patients before and after the surgical intervention in respect to the clinically healthy persons

Competition of disorder and electron-phonon coupling in 2H-TaSe2−x_{2-x}Sx_x (0≤x≤20\le x\le 2) as evidenced by Raman spectroscopy

The vibrational properties of 2H-TaSe$_{2-x}$S$_x$ ($0 \le x \le 2$) single crystals were probed using Raman spectroscopy and density functional theory calculations. The end members revealed two out of four symmetry-predicted Raman active modes, together with the pronounced two-phonon structure, attributable to the enhanced electron-phonon coupling. Additional peaks become observable due to crystallographic disorder for the doped samples. The evolution of the E$_{2g}^2$ mode Fano parameter reveals that the disorder has weak impact on electron-phonon coupling, which is also supported by the persistence of two-phonon structure in doped samples. As such, this research provides thorough insights into the lattice properties, the effects of crystallographic disorder on Raman spectra, and the interplay of this disorder with the electron-phonon coupling in 2H-TaSe$_{2-x}$S$_x$ compounds